Method for removing temporarily emplaced threads from fabric material



United States Patent Office 3 ,3 73,4 7 1 Patented Mar. 19, l 968 ABSTRACT OF THE DISCLGSURE A basting thread formed of polycarbonate with oriented molecular structure and emplaced in a fabric material is subjected to agitation in the presence of perchlorethylene during the dry cleaning of the material and upon being fractured is removed from the material.

The present invention relates to a method for removing specific threads from fabric materials and more particularly to the removal of threads which are temporarily emplaced in the material for manuafcturing convenience and which are not required in the end use of the manufactured product.

For example, in the manufacture of various types of knitted goods a thread, called the drawthread, is frequently employed to hold panels of the goods together until such time as the panels need to be separated and at such time that thread requires removal either by a conventional manual operation, or equivalent. Also, in the manufacture of lace it is customary during manufacture to join a plurality of strips of the lace along confronting side edges by means of a drawthread which can later be removed, chemically or otherwise, when the lace strips are to be separated. In particular, during the manufacture of articles of clothing it is customary to employ various types of basting threads which later require removal. In the copending application of Peter J. Werth, In, and Walter W. King, Ser. No. 375,931 filed June 17, 1964, now US. Patent No. 3,311,928 and assigned to the same assignee as the present invention, certain plastic thread materials and a method for removing the plastic thread from fabrics after it has served its intended basting purposes, are disclosed.

I now have discovered that the inherent property of certain plastic thread, notably of the polycarbonate type, to break when subjected to agitation in the presence of certain dry cleaning solvents may be usefully employed for purposes as above indicated. Accordingly, it is an object of the present invention to provide an improved method for removing temporarily emplaced plastic thread from fabric material by causing fragmentation of the thread in the presence of a drycleaning solution and by separating the fragments from that solution and that material.

The precise phenomena involved in this discovery are not known and the following theory is submitted primarily in order to disclose the most plausible explanation presently available to me. In this connection reference is made to the following examples showing a presently preferred method for carrying out the invention.

Example 1 A batch of polycarbonate available from Mobay Chemical Co. under the trademark Merlon was meltextruded and formed into a mono-filament basting thread. The extruded thread was then drafted, or elongated, under suitable tension until its length was approximately doubled and with a concomitant reorientation of its molecular structure. At this time the thread acquired a diameter of about 0.006 inch and a tensile strength of about 30,000

pounds per square inch. The capability of the finished thread to elongate further when pulled by the sewing machine needle into a fabric was negligible, and with the result that the thread was not left in loose condition when sewn into a fabric material.

Example 2 Fifty-four coats for mens suits were fabricated using for basting purposes the thread disclosed in Example 1. These coats were divided into lots of about ten each and each lot in turn was separately treated after having been placed in the basket of an American Laundry Machinery Co. drycleaning machine type No. 2,209 and tumbled at about 45 rpm. Perchlorethylene at a temperature of about F. was circulated through the machine in contact with the coats and was continually withdrawn through an outlet conduit containing a conventional button trap filter upstream from a conventional diatornaceous earth filter.

Within 20 seconds after the tumbling operation on each lot started fragments of the basting thread began to strike the window of the tumbling chamber. After periods of treatment ranging from four minutes for one lot to fourteen minutes for another lot, the coats of the several lots were spun dry and removed from the machine.

Approximately by weight of the original thread was caught in the form of thread fragments in the button trap filter indicating that a minor fraction only of the thread could have dissolved in the perchlorethylene. In addition, some thread fragments fell from the coats when they were removed from the machine. In coats wherein jump basting had been employed, the length of the thread ragments was substantial; in some instances being about 4-5 cm. in length.

Upon being spun dry, the fabric of the coats was clean, no residue of the thread was observed thereon, and the color of the fabric had not been adversely affected by the treatment.

It is surmised from the examples that the polycarbonate thread in its cylindrical form and in the presence of a suitable drycleaning solvent partakes of the nature of a glassy network polymer subject to diffusion of molecules of the solvent into the thread and as a result, undergoes stress cracking. Contact of the outer surface of the thread with the solvent would appear to cause a swollen shell of thread surrounding and attached to the glassy core portion of thread and to prevent axial swelling of the thread, as an entity. This of course, places a compressive stress on the shell portion and a tensile stress on the core portion. As the swelling front moves inwardly, the tensile stress increases until the tensile strength of the core is reached, at which time the core cracks transversely. While this physical modification of the thread is taking place the fabric containing the thread is being mechanically agitated and such agitation aids in the thread fracturing action. Moreover, the mechanical agitation also serves to shake the fragment of fractured thread from the fabric as soon as fracture occurs.

It is further surmised that in the sewing of the thread into the fabric, the needle movement serves to stress the thread at spaced points along the thread length and that swelling of the shell of thread is pronounced at those points where the needle has exerted its pull on the thread during sewing. Accordingly, the fracturing of the thread will preferentially occur at points where it previously had been subjected to needle stressing.

In accordance with the invention no deliberate cooling of the solvent is required in order to speed up the rate of fracturing of the thread. In fact, it is a feature of the invention that the solvent is used at temperatures normally found in drycleaning processes, and at a temperature of about 75 F. at least. Since the fragments of thread can be caught in the trap usually found on drycleaning apparatus and since the solution initiates the necessary fracturing of the thread at normal temperatures of the solution and also well within the range of cycle times, used on such apparatus, no modification of the drycleaning apparatus is required in the practice of the present invention.

Although the foregoing examples disclose preferred materials comprising the plastic thread and the drycleaning solvent, it will be appreciated that in its broader aspects the invention is not limited to the precise thread and solvent found in those examples.

What is claimed is:

1. The method of removing a thread temporarily emplaced in a fabric material and comprising a polycarbonate plastic thread having its molecules reoriented by elongation of the thread following the initial formation of the thread and including, contacting the thread and the material with perchlorethylene for a sufiicient time to initiate fracturing of the thread, agitating the thread and material while in contact with the perchlorethy'lene thereby to apply mechanical stress to the thread and to shake fragments of fractured thread from the material, and thereafter separating the fragments of thread from the perchlorethylene.

2. The method of claim 1 wherein said time of contact is at least four minutes.

3. The method of claim 1 wherein said perchlorethylene has a temperature of at least 75 F. during its contact with said thread.

References Cited UNITED STATES PATENTS 3,311,928 4/1967 Werth et a1. 28--76 LOUIS K. RIMRODT, Primary Examiner. 

